iOS KVC與KVO的簡單使用

#import "ViewController.h"

#import <Foundation/Foundation.h>

@interface DataModel : NSObject

@property (nonatomic,copy)NSString *stockName;

@property (nonatomic,assign)float price;

@end

@implementation DataModel

@end

@interface ViewController ()

@property UILabel *myLabel;

@property UIButton *myButton;

@property DataModel *model;

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    self.model=[[DataModel alloc]init];

    [self.model setValue:@"searph" forKey:@"stockName"];

    [self.model setValue:@"10.0" forKey:@"price"];

    [self.model addObserver:self forKeyPath:@"price" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];

    self.myLabel=[[UILabel alloc]initWithFrame:CGRectMake(130, 100, 100, 100)];

    self.myLabel.layer.masksToBounds=YES;

    self.myLabel.layer.cornerRadius=50;

    self.myLabel.textAlignment=NSTextAlignmentCenter;

    self.myLabel.textColor=[UIColor cyanColor];

    self.myLabel.backgroundColor=[UIColor grayColor];

    self.myLabel.text=[NSString stringWithFormat:@"%@",[self.model valueForKey:@"price"]];

    [self.view addSubview:self.myLabel];

    self.myButton=[UIButton buttonWithType:UIButtonTypeRoundedRect];

    self.myButton.frame=CGRectMake(130,200 , 100, 30);

    [self.myButton setTitle:@"按鈕" forState:UIControlStateNormal];

    [self.myButton addTarget:self action:@selector(changeValue) forControlEvents:UIControlEventTouchUpInside];

    [self.myButton setBackgroundColor:[UIColor lightGrayColor]];

    [self.view addSubview:self.myButton];

}

- (void)changeValue{

    [self.model setValue:@"20.0" forKey:@"price"];

}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{

    if ([keyPath isEqualToString:@"price"]) {

        self.myLabel.text=[NSString stringWithFormat:@"%@",[self.model valueForKey:@"price"]];

    }

}

- (void)dealloc{

    [self.model removeObserver:self forKeyPath:@"price"];

}

- (void)didReceiveMemoryWarning {

    [super didReceiveMemoryWarning];

}

@end